In applying CMP (Chemical Mechanical Planarization) as a process step in the manufacture of micro-electronic devices such as semiconductor wafers, blanket silicone wafers and computer hard disks, a polishing pad may be used in conjunction with an abrasive-containing or abrasive-free slurry to affect planarization of the surface of the device. To achieve a high degree of planarity of the surface of the device, typically measured in the order of Angstroms, the slurry flow should be distributed uniformly between the surface of the device and the pad. To facilitate such uniform distribution of the slurry, a plurality of grooves or indentation structure may be provided on a polishing pad. The plurality of grooves may have individual groove widths of 0.010 inches to 0.050 inches, depths of 0.010 inches to 0.080 inches and distance between adjacent grooves of 0.12 inches to 0.25 inches, respectively.
While the grooves may provide the above-mentioned benefits, nevertheless, they may not be sufficient to effect local planarization on the die (or single microchip) level on a semiconductor wafer. This may be due to the relatively large differences between the grooves and the individual features, such as interconnects, on the microchip. Advanced ULSI and VLSI microchips, for example, may have feature sizes on the order of 0.35 micrometers (0.000014 inches) that are many times smaller than the width and depths of the individual grooves on the polishing pad. In addition, the feature sizes on a microchip are also thousands of times smaller than the distance between the adjacent grooves, which may result in non-uniform distribution of the slurry on a feature size level.
In an effort to improve upon the uniformity of local, feature-scale planarization, CMP pad manufacturers have, in some instances, provided asperities or high and low areas on the surface of the pads. These asperities may have a size ranged from 20 to over 100 micrometers. While, such asperities may be closer in size to that of the microchip features, as compared to the grooves, the asperities may change in shape and size during the polishing process, and may require continuous regeneration by abrading the polishing pad surface with a conditioner fitted with diamond abrasive particles. The diamond abrasive particles on the conditioner continuously scrape off the surface asperities that are deformed as a result of frictional contact between the pad, the slurry and the surface of the device, and expose new asperities to maintain consistency of planarization. The conditioning process, however, may be unstable, as it may utilize the sharp diamond particles to sever the deformed asperities. The severance of the deformed asperities may not be well controlled, resulting in changes in the size, shape and distribution of the asperities that in turn may cause variation in the uniformity of planarization. Furthermore, the frictional heat generated from conditioning may also contribute to the non-uniformity of planarization, by changing the surface properties of the pad, including properties such as shear modulus, hardness and compressibility.